Spraying lacquer over urethane.

[Burt Pierce]

I just sprayed some 2 part urethane (automotive clearcoat) on a box, and I think to continue with additional coats is beyond my skills. If I sand the urethane, can I spray lacquer over it in order to finish my project?

[Phil Phelps]

I just sprayed some 2 part urethane (automotive clearcoat) on a box, and I think to continue with additional coats is beyond my skills. If I sand the urethane, can I spray lacquer over it in order to finish my project?

What you sprayed is considered "stable" because it has a catalyst. Don't reverse procedure, however. A stable product will attack and dissolve an unstable product.

[Burt Pierce]

Phil,
Do I understand you to be saying that I can spray lacquer on top of the "stable" catalyzed urethane?
Burt

[Jim Becker]

I'm going to suggest that you do not spray solvent-based lacquer over the finish you already applied unless you absolutely test it thoroughly on scrap. Lacquer has a tendency to do nasty things to other finishes with very few exceptions.

[Jim Barry]

Dewaxed shellac is compatible over or under virtually any finish. I use it all the time rather than spend time trying to figure out what is on a piece that I'm refinishing. I usually use Zinnser Seal coat which is a dewaxed, 2lb.cut blond shellac. Other "off the shelf" shellac contains wax. With that said, they can be used if you let it sit for a day or two and then pour off only the solution on top. Don't stir it. The wax will have settled to the bottom.

Spray or brush on a coat, lightly sand and apply the finish of your choice.

[Scott Holmes]

Why do you want to put a less durable finish over a very hard, durable finish?

Another coat of your conv. varnish then you can rub it out to any shine you want.

[Phil Phelps]

Becker and Holmes are correct.
If you are not sure always test. You shouldn't use a product over another without knowing first. An example is alkyd, (oil base), over lacquer. That will work, but lacquer over oil will result in an "alligator" finish. You would need a barrier between the alkyd and lacquer. Usually a catalyzed product is considered stable but I would verify before doing so. I'm not sure a pre-cat lacquer is considered stable.